Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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747 FXCA20 KWBC 181911 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 311 PM EDT FRI OCT 18 2024 FORECAST BULLETIN 18 OCT 2024 AT 1900 UTC: THE NATIONAL HURRICANE CENTER CONTINUES TO MONITOR TWO AREAS OF POSSIBLE TROPICAL CYCLONE FORMATION IN THE ATLANTIC BASIN. ONE SYSTEM IS KNOWN AS AL94...CURRENTLY NEAR 65W...AND THE OTHER IS AN AREA OF LOW PRESSURE IN THE WESTERN CARIBBEAN JUST NORTHEAST OF HONDURAS...NOW KNOWN AS AL95. AS OF THIS WRITING...THROUGH 48 HOURS...THE CHANCE OF FORMATION IS 20 PERCENT FOR AL94...AND 70 PERCENT FOR AL95. THE LATEST GUIDANCE CONTINUES TO SUGGEST THAT THE STRONGEST SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AL94 WILL BE TO THE NORTH OF THE NORTHEAST CARIBBEAN ISLANDS TODAY INTO SATURDAY...AND THIS IS ALREADY BEING OBSERVED ON SATELLITE IMAGERY. THAT SAID...SHOWERS AND THUNDERSTORMS DIRECTLY ASSOCIATED WITH AL94 COULD AFFECT THE TURKS AND CAICOS AS WELL AS THE SOUTHERN BAHAMAS FROM SATURDAY INTO SUNDAY. SATELLITE IMAGERY IS ALSO SHOWING DEEP CONVECTION RELATED TO AL95...AND THE MODEL GUIDANCE IS STARTING TO BE MORE IN AGREEMENT IN TERMS OF RAINFALL OVER NORTHERN CENTRAL AMERICA INTO SOUTHERN MEXICO. ACROSS THE ATLANTIC AND EASTERN TROPICAL REGION...THE TWO SYSTEMS NHC IS MONITORING ARE TAKING CENTER STAGE ON THE RAINFALL POTENTIAL OVER THE AREA. HOWEVER...THERE ARE OTHER SYNOPTIC FEATURES THAT WILL CONTRIBUTE TO THE OVERALL RAINFALL POTENTIAL OVER THE TROPICAL REGION. THE MONSOON TROUGH IS EXTENDING FROM THE PACIFIC INTO THE SOUTHERN CARIBBEAN. THERE IS A BROAD HIGH PRESSURE ACROSS THE EASTERN ATLANTIC. ANOTHER HIGH PRESSURE OVER THE EASTERN USA THAT IS EXTENDING INTO THE GULF OF MEXICO. A LOW PRESSURE IN THE WESTERN ATLANTIC...NEAR 37N/67W WITH A FRONTAL BOUNDARY THAT IS CURRENTLY STATIONARY AND IT EXTENDS FROM THE LOW PRESSURE SOUTHWEST THROUGH THE BAHAMAS...CUBA..AND INTO THE YUCATAN PENINSULA. SATELLITE IMAGERY IS CURRENTLY INDICATING CONVECTION OCCURRING ALONG THE FRONTAL BOUNDARY...WHICH IS BEING ENHANCED BY BROAD MID AND UPPER LEVEL LOWS CENTERED OVER THE WESTERN ATLANTIC...BUT THE ASSOCIATED TROUGH AND STRONG MID AND UPPER LEVEL WINDS EXTEND INTO THE GULF OF MEXICO AND THE WESTERN TROPICAL ATLANTIC. THIS FRONTAL BOUNDARY IS EXPECTED TO REMAIN STATIONARY FROM EAST OF THE BAHAMAS TO AROUND THE YUCATAN PENINSULA TODAY...WHILE FURTHER EAST OF THE BAHAMAS...THE FRONTAL BOUNDARY WILL BECOME A COLD FRONT BY THIS EVENING. BY SATURDAY EVENING INTO SUNDAY...THE FRONTAL BOUNDARY WILL BECOME A COLD FRONT FROM THE TROPICAL ATLANTIC WEST INTO NEAR YUCATAN...THEN STATIONARY IN THE CENTRAL GULF OF MEXICO...AS IT WEAKENS...FRAGMENTING BY SUNDAY NIGHT INTO MONDAY. SHOWERS AND THUNDERSTORMS WILL CONTINUE TO BE EXPECTED ALONG THE FRONTAL BOUNDARY OVER CUBA AND THE BAHAMAS THIS WEEKEND...AS IT INTERACTS WITH THE MID AND UPPER LEVEL TROUGHS...AS WELL AS ALLOWING FOR MOISTURE TO POOL JUST AHEAD OF THE FRONTAL BOUNDARY ACROSS THE TROPICAL ATLANTIC. IN TERMS OF RAINFALL ACROSS THE REGION...THE MODEL GUIDANCE IS IN MORE AGREEMENT NOW COMPARED TO THE PAST FEW DAYS...ESPECIALLY WHEN IT COMES TO THE RAINFALL OVER NORTHERN CENTRAL AMERICA AND SOUTHERN MEXICO. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AL95 ARE DEVELOPING AROUND THE BROAD CIRCULATION...BUT OVERALL DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED ACROSS THE TROPICAL REGION THROUGH THE WEEKEND. ONE PARTICULAR AREA TO NOTE IS AREAS IN AND AROUND CUBA...WHERE THE MODEL GUIDANCE SEEMS TO BE UNDERESTIMATING THE RAINFALL POTENTIAL OVER THE AREA. THE LATEST SATELLITE IMAGERY SHOWS MORE CONVECTION THAN THE MODEL GUIDANCE WOULD HAVE SUGGESTED FOR AREAS NEAR CUBA ALONG THE FRONTAL BOUNDARY. THIS UNDERESTIMATING OF THE RAINFALL IN THE AREA HAS BEEN OBSERVED OVER THE PAST FEW DAYS...FOR THAT REASON OUR RAINFALL FORECAST FOR AREAS IN AND AROUND CUBA IS HIGHER THAN WHAT THE MODEL GUIDANCE IS SUGGESTING. ACCORDING TO THE LATEST GUIDANCE...THE COMBINED 3-DAY RAINFALL FORECAST INDICATES THAT THE AREAS WITH MOST RAINFALL...NOT SURPRISING...WILL BE OVER SECTORS FROM BELIZE TO PORTIONS OF SOUTHERN MEXICO...PARTICULARLY OVER OAXACA AND VERACRUZ. EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC TYPE SOF INT 19/00 19/12 20/00 20/12 21/00 21/12 22/00 22/12 TW 21N 65W 66W 68W 70W 73W 75W 78W 80W 83W A TROPICAL WAVE IS INITIALIZED AT 65W AND TO THE SOUTH OF 21N. THIS WAVE IS EXPECTED TO MOVE WEST. MOST OF ITS CONVECTION AND MOISTURE IS FORECAST TO REMAIN NORTH OF THE GREATER ANTILLES THIS WEEKEND. HOWEVER...THE WAVE AXIS WILL MOVE THROUGH THE CARIBBEAN OVER THE NEXT FEW DAYS...AND WILL HAVE A BAND OF DEEPER MOISTURE MOVE THROUGH THE GREATER ANTILLES AND THE CARIBBEAN THIS WEEKEND. THE NATIONAL HURRICANE CENTER IS MONITORING THIS SYSTEM FOR TROPICAL CYCLONE FORMATION...CURRENTLY WITH A 20 PERCENT CHANCE OF FORMATION THROUGH 48 HOURS AND 7 DAYS. ALAMO...(WPC) $$